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Effect of Methylene Spacers in Poly(methacrylate)s Bearing Styrylpyridine Side Chains on the Ability to Control Liquid Crystal Alignment
Author(s) -
Yamaki Shigeru,
Nakagawa Masaru,
Morino Shin'ya,
Ichimura Kunihiro
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010101)202:2<354::aid-macp354>3.0.co;2-d
Subject(s) - photoisomerization , methylene , side chain , isomerization , chemistry , polymer , photochemistry , methacrylate , liquid crystal , methyl methacrylate , polymer chemistry , dichroism , materials science , organic chemistry , polymerization , catalysis , optics , physics , optoelectronics
The photochemistry, photoinsolubilization and ability to control surface‐assisted liquid crystal (LC) alignment of poly(methacrylates) tethering styrylpyridine (SP) side chains through methylene spacers (m = 2, 6 and 12) are described. The extent of (2 + 2) photodimerization and E‐to‐Z isomerization of SP side chains was markedly affected by the length of methylene spacers. In the early stage of photoirradiation, the photodimerization took place preferentially for SP‐polymers with a shorter methylene spacer, whereas the photodimerization was accompanied by the E‐to‐Z photoisomerization for the polymers with longer spacers even in the early stage of photoirradiation. Irradiation of thin films with linearly polarized light resulted in the generation of dichroism of SP moieties owing to the angular‐selective consumption of E ‐isomer, leading to surface‐assisted homogeneous LC aligment. The direction of LC photoalignment was reversed from perpendicular to parallel orientation when SP moieties were tethered to polymer backbones through spacers. The working mechanism of the alignment reversion was discussed, based on the angular‐selective E‐to‐Z photoisomerization and photodimerization.